The present invention relates to apparatus for use in sterilization of surgical or medical items such as surgical instruments and prosthetic devices. In particular, the present invention relates to a sterilization container suitable for use in conventional steam (i.e., autoclave) or flash sterilization procedures currently used in hospital and surgical techniques for establishing and maintaining sterile conditions for these instruments and devices (collectively referred to as "medical items").
There are a number of different processes for sterilizing medical items which are recognized in the industry as effective, for example, steam sterilization or exposure to radiation or a gas. Even for a given sterilization process, the procedure for effecting sterilization may vary according to the apparatus used.
By way of example, conventional steam (i.e., autoclave) sterilization is widely used in hospital central supply areas where time is not critical. This procedure requires exposure to steam at 250.degree. F. for at least 15 minutes. So-called "flash" sterilization which is more commonly used in operating rooms, subjects the items to higher temperatures (e.g., 270.degree. F.) for a shorter time (three minutes or more) according to well-known and accepted data relating sterilization to these parameters. Another technique, exposure to ethylene oxide (88/12) at a temperature of 120.degree.-140.degree. F. and 20-40% R.H. for a minimum of one hour is also used and is an accepted method for sterilizing medical items.
If the intended use of the sterilized item is in an operating room where flash sterilization is most commonly used, the items and their containers are normally not wrapped, so they may still be hot when it is desired to retrieve or transfer them, thereby requiring special safety procedures for handling.
Other items, such as instruments used frequently or regularly, may be subjected to conventional steam sterilization before their intended use and then stored in a central supply facility. In such a case, provision must be made for maintaining until use the sterile condition that has been achieved.
If it is desired to maintain sterility for some storage period, after conventional steam sterilization, the tray and contents may be wrapped prior to sterilization with a steam-permeable material such as linen or disposable sterilization wrap which will serve as a bacterial filter after sterilization and during storage. Sometimes the surgical item is wrapped separately and placed in the tray, and then the entire tray and contents are wrapped again. Typically, strips of tape are applied to the fully wrapped tray and contents, and dated in some cases, so that supply personnel will know that the parcel has been sterilized and when it was sterilized.
One disadvantage of applying a sterilization wrap is that it may tear or be punctured in handling, thereby violating the sterility of the contents. This is particularly true in the use of metal trays which are containers most widely used currently. In storage, for example, the trays are sometimes slid along metal shelves which contribute to the problem of tearing the wrap.
Another sterilization technique for central supply employs specially designed reusable containers of stainless steel or aluminum which have sealable lids. Although reusable containers provide an impervious barrier to bacteria after sterilization, holes or channels must be provided to admit steam during the process. These holes or channels must be covered with sterilization wrap to prevent contamination. Sometimes mechanical valves are provided which are opened during sterilization and closed thereafter. Because of the impermeability the chance of undesirable water accumulating within the container is increased. Thus, the term "reusable" refers to the fact that the container, which does not require a complete wrap prior to each sterilization, is reusable, although any wrap or filter and even some valves are discarded after use.
A wide variety of apparatus is available for use for sterilizing medical items. Where flash sterilization is employed, typically open stainless steel trays having perforated or metal mesh bottoms are used. These trays are also suitable for complete wrapping with a sterilization wrap and storage in a central supply area. Other apparatus available for use in central supply areas includes a metal container with closable top having both top and bottom perforated for steam penetration.
So-called reusable containers may have an impermeable tray and hinged cover adapted to be closed and thereby seal the contents to obviate the use of a sterilization wrap. A valve may be opened to admit steam during sterilization procedure and then closed to seal the sterilized environment within the container. Alternatively, an opening is provided in the container with a replaceable filter which provides a bacterial barrier during storage.
There are a number of disadvantages associated with the systems and apparatus described above which are currently used to sterilize medical items. One of the more common disadvantages with the apparatus is that of weight. Metal trays, whether stainless steel or aluminum, are heavy. The added weight of instruments makes these trays even more difficult in handling and manuevering.
A second disadvantage is the special precautionary handling procedures required for flash sterilization. Metal has a high heat capacity and the temperature of metal sterilization trays remains high following sterilization. Clamps or cushioned heat pads must be used in handling them immediately following steam sterilization, as previously mentioned. Further, because of the high heat capacity of the trays, they remain cooler than other materials during steam sterilization, and thereby form water condensate for a longer period of time. Condensate may accumulate either in the bottom of the tray, if it is not of the screen mesh type, or, depending upon the shape and nature of the items being sterilized, moisture may accumulate in or on one or more of the items.
Further, where commercially available sterilization wrap is used to completely enclose metal trays, it is susceptible to tearing or puncture, thereby violating the sterility that may have been achieved. This disadvantage is particularly apparent, as mentioned, where a previously-sterilized tray and its contents are stored for later use in a central supply area where handling is likely to be more rough than in an operating room and the wrapped tray is subject to sliding on metal shelving.
The shelf life of a wrapped tray is limited, typically of the order of 30 days. This is considered too short a time for certain items which are infrequently used, thereby requiring special procedures for such items to insure their sterilization prior to use.
Another disadvantage of metal trays having perforated or mesh bottoms is that even stainless steel is subject to corrosive attack or oxidation in the extremely hostile environment of repeated exposure to steam at elevated temperatures.
Reusable container systems, while obviating some of the problems of wrapped trays, have created still further problems. For example, reusable container systems are normally heavier than simple perforated trays. The added weight, of course, makes them more cumbersome in handling and maneuverability. In addition, however, the procedures required for sterilization are considered by some to be too complex, requiring mechanical valves or inserted wrap for use as filters, or other special procedures or techniques depending upon the apparatus. Any one of these special procedures or devices could cause malfunction or simply be forgotten, thereby causing a failure of sterility.
Reusable systems also typically require a large initial investment for a hospital and considerable preliminary evaluation and justification, both from financial and efficacy stantpoints, prior to purchase and installation. Further, due to high manufacturing costs, reusable containers are available only in limited sizes.
Again, depending upon the apparatus of the particular sterilization system, if it is reusable particularly, a new system of this type may require retraining of personnel.